(a) Technical Field
The present disclosure relates generally to wirelessly charging electric or hybrid electric vehicles, and more particularly, to an interoperable electric vehicle wireless charging method and system.
(b) Background Art
Recently, technology relating to electric vehicles (EVs) and hybrid electric vehicles (HEVs) has been rapidly developing. EVs and HEVs are powered, at least in part, by electricity, and these vehicles often collect and store electricity, or in other words, are charged, from off-vehicle sources. As such, various methods of charging EVs and HEVs have been explored. In particular, techniques for wireless charging, or inductive charging, have been the subject of considerable research.
Wireless charging, as opposed to wired charging, improves durability and longevity of the charging components by limiting contact and exposure of the components, increases safety by concealing potentially dangerous wires and connection interfaces, and enhances versatility by allowing charging stations to be implemented in a variety of ways (e.g., as a portable charging pad, embedded in a parking lot or road, etc.). To this end, wireless charging relies on an electromagnetic field to transfer energy between a charging station (e.g., wireless charging assembly) and an electrical device, such as a smart phone, a laptop, or an electric vehicle, as in the present case. Energy is sent through an inductive coupling formed between the wireless charging assembly and the device. Typically, an induction coil in the wireless charging assembly (e.g., primary coil) uses electricity, often provided from the power grid, to create an alternating electromagnetic field. An induction coil in the electrical device (e.g., secondary coil) may then receive power from the generated electromagnetic field and convert it back into electrical current to charge its battery. As a result, the primary and secondary induction coils combine to form an electrical transformer, whereby energy can be transferred between the two coils through electromagnetic induction.
Notably, the secondary coils installed in wireless charging-capable vehicles come in myriad sizes with varying ground clearance amounts (i.e., the distance from the secondary coil to the ground). Difficulties can arise, therefore, as the varying types of secondary coils cause incompatibilities with certain charging systems. For instance, as the ground clearance of the secondary coil increases (e.g., in a vehicle with a relatively high undercarriage), and the magnetic air gap (the vertical distance between the primary coil of the wireless charging system and the secondary coil of the vehicle) also increases, the energy emitted by the primary coil must increase, as well, in order to efficiently charge the vehicle. This is because the radius of the primary coil (as well as the size of the primary coil) is directly proportional to the air gap that can be overcome in order to perform magnetic resonance energy transfer with high efficiency. Consequently, in the case of a larger magnetic air gap (e.g., in a pick-up truck or sports utility vehicle (SUV) having a high ground clearance), some primary coils may be too small to emit the requisite energy to the vehicle. At the same time, larger primary coils may emit unnecessary amounts of energy in the case of a smaller magnetic air gap (e.g., in a sports car having a low ground clearance), resulting in wasted energy.